In an electronic device operating at radio frequencies or microwave frequencies, certain circuit components may emit electromagnetic fields that amount to interference to other circuit components in the vicinity. Such unimpeded electromagnetic interference may degrade the performance of a wireless communications transmitter incorporated into a base station, for example. In some cases, if electromagnetic interaction between the circuit components is severe, an amplifier may become unstable from an electromagnetic feedback path and go into undesired oscillation. In other situations, the electromagnetic interference may degrade amplifier performance by causing inter-modulation distortion or by spreading the bandwidth of the transmit signal beyond its desired boundaries. Inter-modulation distortion refers to unwanted mixing that can occur between two signals at different frequencies within electronic circuitry.
To alleviate the foregoing problems, manufacturers have used what are commonly referred to as can shields mounted on printed circuit boards to electromagnetically isolate circuit components from one another. The prior designs of electromagnetic shields often address frequencies lower than one Gigahertz (1 GHz) because of the prevalent use of these lower frequencies in wireless communication systems over the last 20 years. However, as wireless systems are now licensed to use higher frequencies such as those greater or equal to 1.8 Gigahertz for personal communication services (PCS), some of the earlier shield designs do not provide adequate isolation between different components of a printed circuit board. Thus, a need exists for an electromagnetic shield that is applicable to printed circuit boards operating at microwave frequencies or at other frequencies.